Electronic engine controls comprise electronic circuitry, typically microprocessor based, that processes various inputs to provide the desired engine control functions Usage of electronic engine controls has become commonplace in internal combustion engines that power automotive vehicles.
Certain engine-powered vehicles have one or more PTOs (power take-offs) for allowing equipment or machinery other than the vehicle itself to be operated by the engine, and such vehicles require an associated control for controlling engine operation, engine speed for example, when a PTO is in use operating a piece of equipment If the associated control has multiple control stations, and/or if multiple pieces of equipment are to be controlled, it is desirable to minimize the risk that conflicting inputs from the associated control resulting from human operator error or inadvertence will affect engine and/or equipment operation. Accordingly, it has heretofore been known to provide equipment interlocks using electromechanical relay circuits that give control priority to a request for control from a first-to-be-actuated of multiple control-request switches (These control-request switches may sometimes hereinafter also be referred to as control-enable switches.) If a second-to-be-actuated of the multiple control-request switches requests control before the request from the first-to-be-actuated control-request switch has been withdrawn, the request from the second-to-be-actuated control-request switch will be denied. The same will be true for any other control-request switch so long as the first-to-be-actuated control-request switch retains control.
The present invention relates to a new and useful interlock circuit that prevents associated controls from commanding potentially conflicting operation of an engine and/or of equipment that is powered from the engine through one or more power take-offs. One important advantage of the invention is that fewer relays are used than in the prior relay-type interlock, and this in turn means that wiring complexity is reduced because there are fewer circuits and wiring connections. Reductions of this nature can improve productivity and reliablity. The invention is intended to assist in guarding against human operator error that might otherwise cause potentially conflicting requests to be given to the engine and/or equipment powered from the engine via a PTO.
Briefly, the present invention may in one way generally be described as an interlock circuit that detects actuation of various control-request switches and enables control by the first-to-be-actuated of multiple control-request switches. Subsequent actuation of a second-to-be-actuated control-request switch terminates the enablement of control, which is accompanied by the engine going to a default mode of operation (shut-down or idle are possibilities depending upon how the default is programmed into the engine control) and/or shutting down and locking out equipment powered by the engine.
The invention is further characterized by a unique organization and arrangement of standard electronic circuit components that provide an electronic interlock circuit between the control-request switches and the electronic engine control. The circuit is powered by available electric power, typically 12 VDC.
The foregoing, along with further features, advantages, and benefits of the invention, will be seen in the ensuing description and claims, which are accompanied by drawings. The drawings disclose a presently preferred embodiment of the invention according to the best mode contemplated at this time for carrying out the invention.